1. Field of the Invention
The present invention relates to an electric drive steering locking apparatus.
2. Description of Related Art
This kind of electric drive steering locking apparatus includes a locking member that engages with and disengages from a steering shaft, a motor that actuates the locking member, a motor driving control unit that controls a current supplied to the motor and switches polarities of the current, and a microcomputer that causes the locking member to perform locking actuation and unlocking actuation through the motor driving control unit and the motor. During an engine operation, the locking apparatus maintains an unlocking situation to enable the steering. On the other hand, during the engine stop, the locking apparatus maintains a locking situation to disable the steering.
However, in the electric drive steering locking apparatus, when the motor driving control unit breaks down in an on-actuation state to cause the locking member to perform the locking actuation, the steering is disabled to generate a probability leading to a large accident.
For example, in Japanese Patent Publication Laid-Open No. 2003-63354, a switch is provided on a feeding route from the power supply to the motor, and the power is not supplied to the motor by the switch during driving of the vehicle. Therefore, even if the on-breakdown is generated in the motor driving control unit, the locking member is prevented from mistakenly engaging with the steering shaft during driving.
However, the electric drive steering locking apparatus of Japanese Patent Publication Laid-Open No. 2003-63354 cannot deal with a case in which the motor that actuates the locking member breaks down. In the state in which the motor breaks down, because the electric drive steering locking apparatus cannot be actuated, the steering shaft cannot be unlocked.
In order to prevent a trouble caused by the breakdown of the motor, it is necessary to periodically check the existence or non-existence of the breakdown of the motor. For example, it is conceivable that, before the motor is driven, a current is passed to an extent in which the motor is not actuated and the existence or non-existence of the breakdown is checked by determining an internal resistance value of the motor. However, in the electric drive steering locking apparatus of Japanese Patent Publication Laid-Open No. 2003-63354, both electrodes of the motor are connected to the power supply side or the ground side to put the motor into the stop state. Therefore, it is difficult to pass the breakdown checking current through the motor in the stop state, and the breakdown of the motor cannot be checked.